Helicopter propeller



FIG. 1 is a top view of a helicopter propeller;

FIG. 2 is a side view of the helicopter propeller;

FIG. 3 is a perspective side view of the helicopter propeller; and,

FIG. 4 is an opposite perspective side view of the helicopter propeller.

Broken lines are for illustrative purposes only and form no part of the claimed design. 

The ornamental design for a helicopter propeller, as shown and described. 